Successful waterborne acrylic, or latex emulsion, coating compositions must deliver performance comparable to traditional solvent-borne coatings, while meeting increasingly stringent VOC (volatile organic compounds) emission regulations. Many latex emulsion polymers utilized in latex paints do not coalesce at or near room temperature. The formation of a latex film can be facilitated by incorporating a coalescing agent in the latex emulsion. These coalescing agents, or coalescents, facilitate the individual latex particles coming together to thereby form a continuous film at a given temperature by reducing the minimum film-forming temperature (MFFT) of the latex emulsion polymer.
Traditional coalescents are sometimes described as fugitive coalescents since they tend to escape from the coating film over time. As a result, in some jurisdictions, such coalescents are regulated as VOCs, or volatile organic compounds. A need therefore exists for a non-fugitive coalescent that is capable of meeting the VOC regulations imposed on the paint industry.
To meet VOC regulations, higher molecular weight coalescents may be used to aid in film formation. Unfortunately, these coalescents typically remain in the film and plasticize, that is, reduce the hardness, of the final coating. Further, the coalescents may contribute an unpleasant smell to the paint. Based on these considerations, there is a demonstrated need for less volatile and low-odor coalescing agents that improve coalescence but do not reduce the hardness of the final coating. It would be an additional advantage if the coalescents were reactive, such that they might even increase the hardness of the final coating.
U.S. Pat. No. 3,197,500 discloses methods of making 2,2,4-trimethyl-3-ketopentanoates via the reaction of 2,2,4,4-tetramethyl-1,3-cyclobutanedione with alcohols under basic catalysis. The resulting molecules are said to be valuable for use in perfumery because of their desirable odor and their odor persistence qualities.
U.S. Pat. No. 3,214,461 discloses methods of making 2,2,4,4,-tetraalkyl-3-oxobutyric acid esters said to be useful as plasticizers for cellulose esters and other polymeric plastic substances. The methods are also said to be useful for esterifying and thereby stabilizing proteins. One of the esters, the 2,2,4-trimethyl-3-oxovaleric acid ester of α-methyl-d-glucoside, was found to be compatible with, and to give a good film with, cellulose acetate-butyrate of ½-sec. viscosity, in equal proportions.
There remains a need for less volatile and low-odor coalescing agents that improve the coalescence of latex emulsion films but do not reduce the hardness of the final coating. It would be an additional advantage if the coalescents were reactive, such that they might even increase the hardness of the final coating when cured.